<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box{
      border: 1px solid black;
      overflow: hidden;
    }
    .box1{
      width: 100px;
      background-color: red;
      margin-bottom: -2000px;
      padding-bottom: 2000px;
      float: right;
    }
    .box2{
      width: 100px;
      margin-bottom: -2000px;
      padding-bottom: 2000px;
      float: left;
      background-color: blue;
    }
    span{
      border: 10px solid #111;
    }
  </style>
</head>
<body>
  <div class="box">
    <div class="box1"><p>1233</p><p>1233</p><p>1233</p><p>1233</p><p>1233</p><p>1233</p><p>1233</p><p>1233</p><p>1233</p><p>1233</p></div>
    <div class="box2"><p>1233</p></div>
  </div>
  <span>1</span>
</body>
</html>